1. Technical Field
The present disclosure relates to reminder circuits, and particularly to a power-saving reminder circuit to remind users to shut off commercial power after a computer is powered off or suspended.
2. Description of Related Art
In a personal computer (PC) system, power management is adopted to conserve energy. While the PC is powered, it can be put in a sleep mode to save energy when not in use. System power states derived from the advanced configuration and power interface (ACPI) specification are defined as follows:
S0/Working—The central processing unit (CPU) is fully up and operating; devices are powering up and down as needed.
S1—The CPU is stopped; the random access memory (RAM) is refreshed; the system is operating in a low power mode.
S2—The CPU has no power; the RAM is refreshed; the system is in a lower power mode than S1.
S3—The CPU has no power; the RAM is in slow refresh; the power supply is generally in a reduced power mode (for example, the power supply not supplying much power and is operating in a lower power efficiency mode).
S4—The hardware is completely off; the system memory has been saved to disk.
S5/Off—the hardware is completely off; the operating system has shut down; nothing has been saved.
When the computer is suspended and in the S3, the power supply is generally in a reduced power mode and still consumes energy. When the computer is powered off and in the S5/off state, there is still a +5 volt standby voltage (+5VSB) applied to the motherboard for driving a basic power source control circuit of the computer system during the off state. However, this means the computer still consumes energy in the suspended state or even in the off state, thus, commercial power needs to be shut off to the computer, to save power, but users often forget to do this, resulting in wasting energy.